1. Field of the Invention
The present invention relates generally to the deposition of a silicon nitride film and, more particularly, to a system and method for sputtering a tensile silicon nitride film.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
As most people are generally aware, microprocessors are essentially generic devices that perform specific functions under the control of software programs, which may be stored in one or more memory devices that are coupled to the microprocessor and/or other peripherals. These microprocessors and memory devices generally include many different types of integrated circuits that are typically fabricated from one or more semiconductor materials. The integrated circuits work together to enable the microprocessor and/or memory device to carry out and control various functions within an electronic device. The integrated circuits are typically fabricated on a semiconductor wafer surface through any number of suitable manufacturing processes. One of these manufacturing processes is known as “layering.” Layering generally refers to adding material to the surface of the wafer by a growth process, such as oxidation, or through a deposition process, such as chemical vapor deposition (“CVD”) or physical vapor deposition (“PVD”), which is also referred to as “sputtering.”
One of many suitable layers that may be added to the surface of the wafer is a silicon nitride (“SiN”) film. There are a variety of suitable and beneficial uses for SiN films in the fabrication of integrated circuits. For example, SiN films may be employed to create a final passivation layer to cover a completed integrated circuit to protect the underlying integrated circuit and its components. In addition, SiN films may also be used as interdielectric layers in multimetallization schemes, as insulation between polysilicon and metallization layers, as doping barriers, as diffusion sources, as isolation regions, and/or as part of silicon gate structures.
For a variety of applications, it is beneficial to deposit the SiN film at or around room temperature to minimize the possibility of heat-related damage to any metal layers beneath the SiN film. Until recently, the only techniques for depositing room temperature SiN films were via fairly inefficient CVD processes. Recent advances, however, have facilitated the deposition of SiN films using PVD or sputtering. In sputtering, a working gas, such as argon, is introduced into a process chamber that contains the wafer to be layered and a slab of the desired film material (known as a “target”). Some form of electricity is then used to ionize the atoms of the working gas. The ionized gas atoms are then attracted to the target. When the ionized gas atoms strike the target, they “knock off” atoms from the target. These knocked off atoms then fall 5 towards the bottom of the process chamber where they are deposited on the surface of the wafer to create a film.
Disadvantageously, however, the sputtering of SiN films is generally still limited to sputtering SiN films with compressive stress. As those of ordinary skill in the art will appreciate, films under compressive stress have a negative film stress and, as such, tend to bend underlying layers of the integrated circuit in a convex shape. For a variety of applications, however, a tensile SiN film (a SiN film with a positive film stress that tends to bend underlying layers in a concave shape) would be advantageous. For example, negative channel metal oxide semiconductor (“NMOS”) gate structures constructed with tensile SiN films perform better than similar ones constructed with compressive SiN films. As such, a system and method for sputtering a tensile SiN film would be desirable.